Double focus X-ray tube



March s, 1938. QWLAN HANS I 2,110,604

DOUBLE FOCUS X-RAY TUBE Filed Aug. 24, 1935 2 Sheets-Sheet l INVENTOR.

011 [/4/1 6/1fl/1 J ATTORNEY.

O. W. LANGHANS DOUBLE FOCUS X-RAY TUBE Filed Aug. 24, 1935 2 Sheets-Sheet 2 L3fi INVENTOR.

0. W ZA/Vfifl/INS ATTORNEY.

March 8,, E938 Patented Mar. 8, 1938 PATENT OFFICE DOUBLE FOCUS X-RAY TUBE Otto William Langhans, Bloomfield, N. J., assignor, by mesne assignments, to Westinghouse Electric and Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 24, 1935, Serial No. 37,697

' 6 Claims. (01150 -25) My invention relates to X-ray apparatus and particularly to such apparatus employing an X- ray tube known to the art as the double focus type.

X-ray tubes of this general type are known to the art for producing focal spots of different area which are utilized by the Roentgenologist for diagnostic purposes. For example, in the making of fluoroscopic examinations a focal spot of small area is-employed for the purpose of producing as much detail as possible in the resulting image portrayed upon the fluorescent screen. Accordingly the area of the tungsten target impinged by the electrons coming from the thermionic cathode is comparatively small with the result that the generated X-rays are confined to a small area. 7

In the making of radiographic exposures a larger focal spot is produced on the surface of the anode with a resultant increase in the area of the emitted X-ray beam. This necessity for the production of different focal spots accordingly requires the employment of separate X-ray tubes or a single tube capableof producing a large and small focal area by the utilization of cathodes of different size. Moreover, some provision must be made to energize the desired cathode which gives the appropriate focal spot so that no possibility of error occurs on the part of the operator.

It is accordingly an object of my present invention to provide an X-ray apparatus wherein a double focus X-ray tube is employed having different size cathodes which may be alternately 1 energized at will by the operator.

Another object of my present invention is the provision of an X-ray apparatus wherein an X- ray opaque casing surrounds an X-ray tube of the double focus type having thermionic catha odes of different size and one of the cathodes is energized at a time so as to produce a desired focal spot upon rotation of the X-ray tube in its casing.

Another object of my present invention is the provision of an X-ray apparatus employing an X-ray tube of the double focus type wherein the tube is rotatably supported within an X-ray opaque casing and upon rotation of the tube to various positions its respective thermionic cathodes are energized so as to produce a focal spot of the desired area as well as a visual indication being given to the operator of the comparative size of the focal area produced by the particular selected cathode.

Still further objects of my presentinvention will become obvious to those skilled in the art by reference to the accompanyingdrawings where Figure 1 is a side view of an X-ray apparatus constructed in accordance with my present invention,

Fig. 2 is a sectional view on enlarged scale of the apparatus as shown in Fig. 1,

Fig. 3 is a sectional View taken on the line III--III of Fig. 2,

Fig. 4 is anend view of the anode of the X-ray tube taken on the line IV-IV of Fig. 2 and looking in the directionindicated by the arrows, and

Fig. 5 is an end View of the cathode electrode of the X-ray tube taken on the line V--V of Fig. 2 and looking in the direction indicated by the arrows.

Referring now to the drawings in detail I have shown in the several figures an X-ray opaque shield or casing 5 which may be of lead glass or a phenolic condensation product impregnated with a high atomic weight material or having a lining of such material as lead or the like. This casing 5 may be formed of two bell shaped members suitably joined together, as by means of cap screws 6, and formed with an opening constituting a window 1 perviousto X-rays. A cone 8 may be arranged to engage the casing 5 in any suitable manner and serves the purpose of directing the X-rays emerging from the X-ray tube through the pervious window I. One end of the casing 5 is closed and co-axially disposed relative to the longitudinal axis of the casing is an electrical terminal 9 having a spring contact member I0. A similar terminal I2 is also provided in the closed end of the casing which is disposed adjacent the perimeter of the latter. These terminals 9 and I2 are adapted to be engaged by electrical conductors I3 and I4 extending from a suitable source of low tension heating current as well asone of these conductors supplying one side of high voltage potential for the energization of an X-ray tube.

I The cable containing the conductors I3 and I I passes through an insulated cap I5 which threadedly engages the closed end of the casing 5 thus forming a shield for the exposed ends of these terminals. An X-ray tube I6 is rotatably mounted within the casing 5 which tube is .of the double focus type being provided with a thermionic cathode I1 and a similar cathode I8, the latter of which is, as shown, of smaller area than the cathode" I'|.' Both these thermionic cathodes are recessed within a suitable metallic member I9 which forms focusing cups for the respective thermionic cathodes.

A plurality of leading-in conductors pass through the usual press portion 2|] of the X-ray tube and one of these leading-in conductors 22 is connected to one end of each of the thermionic cathodes I1 and I8 as well as to the member I9, while the leading-in conductor-23 is connected to the remainingend of the smaller thermionic cathode I8. Similarly the leading-in conductor 24 is connected to the remaining end of the larger thermionic cathode I! and these latter leading-in conductors 23 and 24 are suitably insulated from the metallic member [9 by extending through enlarged openings 25 provided therein.

The cathode end of the X-ray tube is provided with a base 26 of suitable insulating material having a plurality of contact members. 21, 28 and 29 embedded therein. The contact member 28 is co-axially disposed relative to the longitudinal axis of the Xray tube and is connected to the leading-in conductor 22 and thus to one end of both the thermionic cathodes I1 and I 8. In a similar manner the contact terminals 21 and 29 which are disposed adjacent the periphery of the base member 26 are connected to the remaining leading-in conductors 23 and 24 and thus to the remaining ends of the respective cathodes I! and I8. The spacing between the centrally disposed contact terminal 28 .and the outer contact terminals 2! and 29 is similar to that between the contact terminals 9 and I2 of thecasing so that contact is established between the contact terminals 9 and 28 at .all times when the X-ray tube is positioned within the casing and the casing contact terminal l2 establishes engagement with either of the contact terminals 21 and 29 of the 7 X-ray tube as hereinafter more fully explained.

The base 26 is provided with a peripheral groove 30 which extends approximately 180? around the base and a suitable set screw or the like 32 is provided in the casing which extends into the peripheral groove 30 so as to limit rotation of the X-ray tube to 180. The anode electrode 33 of the X-ray tube is formed of a good heat conducting material, such as copper, and embedded in the surface thereof adjacent the thermionic cathodes is a pair of angularly disposed targets 34 and 35 formed of suitable refractory material, such as tungsten. The larger target 34is disposed opposite the larger area thermionic cathode I! so as to be impinged by the electrons flowing from the latter upon energization thereof, and similarly the smaller area target 35 is disposed opposite to the thermionic cathode l8 for the same purpose.

The anode 33 is provided with a stem 36 of the same material as the anode itself which extends exteriorly of the casing 5 through an open end thereof and is provided with a cooling radiator 31 for the purpose of dissipating the heat generated at the anode due to the impact of the electrons during operation of the tube. To assist in rotating the tube a member 38 may be provided constituting a wing nut or the like so as to be readily gripped by the operator for the purpose of rotating the tube. ode of the X-ray tube frictionally engages the casing 5 and thus forms a bearing for this end of the tube while the anode end may be supported by a collar or the like 39 formed of cork or other suitable material constituting a bearing for the:

anode end of the X-ray tube. V

A window 40 is also provided in the casing 5 which Window registers with indicia provided on the base 26 so that as the tube is rotated from one position to .another the lettering of flarge or small corresponding to the particular thermionic cathode energized from the cathode heating source will be indicated. Due to the tube terminal 28, as before stated, always remaining in contact with the casing terminal 9 and particularly the spring clip In, when the tube is in V the position shown in Fig. 2, the tube terminal 29 will establish engagement with the casing ter- The base 26 provided on the cathminal l2 so that the smaller thermionic cathode l8 receives heating current through the conductors l3 and M as well as the leading-in conductors 22 and 24. At the same time the smaller area tungsten target 35 aligns with the X-ray pervious window I and the electrons impinging on the anode target 35 causes the generation of X-rays which emerge through the pervious window I. The indiciurn small will also register with the opening or window 40 in this position of the tube to thus indicate to the operator that the smaller thermionic cathode is energized and that a corresponding small area focal spot is being produced by the Xrays flowing through the window I from the target 35.

When it is desired that the X-ray tube be employed for diagnostic purposes requiring la larger focal area the operator need only rotate the X- ray tube 180 by gripping the member 38. Such rotation causes a disengagement of the casing terminal l2 and the tube terminal 29 and an engagement of the terminal 2! with the terminal i2. This accordingly enables the larger thermionic cathode I! to be energized from the oathode heating source to which the conductors l 3 and M are connected.

Simultaneously the larger area anode target 34 is rotated to a position where the same .aligns with the X-ray pervious window I so that the X- rays generated by impact of the electrons flow ing from the larger area thermionic cathode I'I emerge from the tube and casing through the window 7 in the same manner as previously described.

7 Again the indicium large inscribed or stenciled upon the base member 26 will register with the window 40 and the indicium small will be moved away from this window thus apprizing the operator that the larger area thermionic cathode is now energized with the resulting production of a larger focal spot. Moreover the peripheral groove 39 into which the set screw 32 extends so limits rotation of the tube that one or the other of the tube terminals 21 or 29 always engages the casing terminal l2, and as the terminal 28 remains in fixed engagement with the terminal 9 one or the other of the thermionic cathodes is energized and at the same time one or the other of the ,anodetargets aligns with the X-ray pervious window.

It thus becomes obvious to those skilled in the art'that I have provided an X-ray apparatus employing an X-ray tube of the double focus type wherein the X-ray tube is rotatably supported within an X-ray opaque casing and upon rotation of the tube to various positions one or the other of the thermionic cathodes will be alternately energized. Simultaneously with rotation of the'tube one or the other of the anode targets aligns with the X-ray pervious window provided in the casing so that the generated X-rays produce the requisite focal area or spot required for the particular diagnostic examination. Furthermore, a visual indication is given to the operator apprizing him of the relative size of the focal spot generated upon energization of either of the thermionic cathodes at any given period.

Although I have shown and described one specific embodiment of my invention I do not desire to be limited thereto as various other modifications of the same may be made without departing from the spirit and scope of the appended claims.

What is claimed:

1. An X-ray apparatus comprising an X-ray opaque casing having an X-ray pervious window therein for the emergence of X-rays, an X-ray tube rotatably supported within said casing and provided with an anode having a plurality of targets and a plurality of thermionic cathodes of different size for producing dissimilar focal areas upon the respective targets, means disposed exteriorly of said X-ray tube and connected to said thermionic cathodes, and means carried by said casing connected to a suitable source of heating current and alternately engageable by portions. of said first mentioned means to cause energization of one of said thermionic cathodes at a time upon rotation of said X-ray tube to align either of said anode targets with said X-ray pervious window.

2. An X-ray apparatus comprising an X-ray opaque casing having an X-ray pervious window therein for the emergence of X-rays, an X-ray tube rotatably supported within said casing and provided with an anode having a plurality of targets and, a plurality of thermionic cathodes of different size for producing dissimilar focal areas upon the respective targets, means disposed exteriorly of said X-ray tube and connected to said thermionic cathodes, means carried by said casing connected to a suitable source of heating current and alternately engageable by portions of said first mentioned means to cause energization of one of said thermionic cathodes at a time upon rotation of said X-ray tube, and means carried by said casing and cooperating with said X-ray tube to limit rotation of said X-ray tube for the purpose of aligning either of said targets with said X-ray pervious window and enabling the alternate energization of said thermionic cathodes.

3. An X-ray apparatus comprising an X-ray opaque casing having an. X-ray pervious window therein for the emergence of X-rays, means carried by said casing and connected to a suitable source of heating current, an X-ray tube supported by said casing for rotation therein and provided with an anode having a plurality of angularly disposed targets and a plurality of thermionic cathodes of different size adapted to be independently heated for producing focal spots of different areas upon the respective targets, means disposed exteriorly of said X-ray tube and connected to said thermionic cathodes with a portion of said means being engageable with said first mentioned means for energizing one of said thermionic cathodes upon rotation of said X-ray tube to one position, and said portion of said last mentioned means being disengaged from said first mentioned means and the remaining portion thereof engaging said first mentioned means upon rotation of said X-ray tube to another position, and means carried by said casing and cooperating with said X-ray tube to limit rotation of said tube in order that only one of said anode targets is: aligned with said pervious window and one of said thermionic cathodes is energized at a time.

4. An X-ray apparatus comprising an X-ray opaque casing having an X-ray pervious window therein for the emergence of X-rays, an X-ray tube supported by said casing for rotation therein and provided with an anode having a plurality of angularly disposed targets and a plurality of thermionic cathodes of different size adapted to be independently heated for producing focal spots of different areas upon the respective targets, a base carried by one end of said tube provided with a plurality of contact terminals connected to said thermionic cathodes, a pair of contact terminals carried by said casing and connected to a suitable source of heating current and engageable by at least two of the contact terminals carried by said base for energizing one of said thermionic cathodes upon rotation of said X-ray tube to one position, and one contact terminal of said pair being disengaged from one contact terminal of said base and engageable with another contact terminal of said base upon rotation of said X-ray tube to another position, and means carried by said casing and cooperating with said tube to limit rotation of said tube in order that only one of said anode targets is aligned with said pervious window and one of said thermionic cathodes is energized at a time.

5. An X-ray apparatus comprising an X-ray opaque casing having an X-ray pervious window therein for the emergence of X rays, an X-ray tube rotatably supported within said casing and provided with an anode having a plurality of targets and a plurality of thermionic cathodes of different size for producing dissimilar focal areas upon the respective targets, means disposed exteriorly of said X-ray tube and connected to said thermionic cathodes, means carried by said casing connected to a suitable source of heating current and alternately engageable by portions of said first mentioned means to cause energization of one of said thermionic cathodes at a time upon rotation of said X-ray tube to align either of said anode targets with said X-ray pervious window, and indicia carried by said first mentioned means and registering with an opening provided in said casing to indicate the relative size of the focal area produced by the particular cathode which is connected to said last mentioned means by rotation of said X-ray tube.

6. An X-ray apparatus comprising an, X-ray opaque casing having an X-ray pervious window therein for the emergence of X-rays, an X-ray tube rotatably supported within said casing and provided with an anode having a plurality of targets and a plurality of thermionic cathodesof different size for producing dissimilar focal areas upon the respective targets, means disposed exteriorly of said X-ray tube and connected to said thermionic cathodes, means carried by said casing connected to a suitable source of heating current and alternately engageable by portions of said first mentioned means to cause energization of one of said thermionic cathodes at a time upon rotation of said X-ray tube, means carried by said casing and cooperating with said X-ray tube to limit rotation of said X-ray tube to align either of said anode targets with said X-ray pervio-us window and enabling the alternate energization of said thermionic cathodes, and indicia carried by said first mentioned means and registering with an opening provided in said casing to indicate the relative size of the focal area produced by the particular cathode which is energized upon rotation of said X-ray tube.

OTTO WILLIAM LANGHANS. 

